Pumping loss was the wrong term I used actually ( a bit rusty been too long out of uni). But I see you knew what I was saying and addressed it appropriately. I am aware that the power increase of hotter combustion may overcome the extra work to compress hotter air but it depends on the power and temperatures we are talking about. I didn't address that part because I didn't want to divert too much. I really wanted to know when is the best point in the cycle to apply pre-heat and what order of temperatures are needed.gruntguru wrote:The pumping losses do not increase with reduced intercooling. The compressor work increases but turbine work increases by the same amount or more. The piston work on the compression stroke increases but the work recovered on the power stroke increases by the same amount or more.PlatinumZealot wrote:But would you want to increase pumping losses (the piston pumping hotter air)? And we have to know what order of temperatures are actually needed. Supposed a paltry 90*C is not enough? Supposed 200*C is not enough? I am just basing this on the GM HCCI video where they use recirculated exhaust gas (900*C) to preheat the air. Supposed after mixing the temperature you need is 300*C? this would be too far above what the compressor can produce. I mean, I don't know what actual temperature is required, but I think this would determine whether you can use that hot intake air injection method or some other method.
The temperature required for auto ignition can be reduced by varying other factors (cetane number, CR, AFR etc etc). Varying the charge air temperature or EGR is more of a "trim" measure to adjust the combustion parameters for different operating points.
Maybe I am a bit behind the times in this here forum so I will read the link you posted in the Renault engine thread to see if I can get some of the questions answered. http://energy.gov/sites/prod/files/2014 ... 09_dec.pdf